The scientific tourist #124 — Edmontosaurus

This week’s image is of an Edmontosaurus at the Denver Museum of Nature and Science:

Edmontosaurus was a late genus of hadrosaurid (duck-billed) dinosaur, living just prior to the K-T extinction of the non-avian dinosaurs. It was also among the largest of the family, growing up to 13 meters (43 ft) long, and weighing about 4 metric tons. Based on the locations of a wealth of recovered fossils, Edmontosaurus was widely distributed but lived near coasts. Studies of its skull indicate it was almost certainly a land dweller and ate dryland plants (in contrast to the pre-1960 concept of it being largely aquatic, with a duck-like diet of soft water plants).

As you can imagine, it would have taken a considerable amount of food to support such a bulky animal — and fortunately Edmontosaurus was well equipped for life as a herbivore. Its duck-like bill could easily clip off vegetation up to 4 meters off the ground, which was then chewed by an array of teeth in the back of its mouth (a big evolutionary advance, compared to the other herbivores of the time). A recent study of microscopic scratches on an Edmontosaurus‘ teeth suggests that hadrosaurs had an approach to chewing unlike that seen in any living animal. Rather than having a flexible lower jaw joint (as seen in today’s mammals), hadrosaurs had hinges between their upper jaws and the rest of their skulls. So when they chewed, the upper jaws pushed outwards and sideways as the upper teeth slid against the lower jaw’s teeth.

This particular skeleton also has one more story to tell us — if you look carefully, you can see a notch in the top middle of its tail. This is a partially-healed bite mark, and given that the top of the tail would normally be at least 2.9 meters (9.5 ft) off the ground, likely the result of a close escape from a T-Rex.